Factors Affecting the Apparent Activity and Heat Sensitivity of Xanthine Oxidase in Milk

Abstract

The xanthine oxidase activity, expressed as ~l OJml/hr, was measured by the Warburg manometric technique. The activity in fresh milk increased as a result of storing at 4 C, heating to 70 C for 5 rain, homogenization, and incubation with commercial enzymes of proteolytic and lipolytic nature. These increases were accompanied by increases of activity in the skimmilk phase, with a corresponding decrease of activity in the fat phase. The changes in apparent activity were attributed to the release of aggregates of enzyme mierosomes from the fat globule membrane.